多天线系统的电磁耦合及干扰特性研究

多天线系统是5G的核心技术.无论是基站侧还是终端侧,多天线系统已经成为不可逆转的技术趋势.由于实际应用场景的限制,多天线系统的物理口径受到限制,天线单元之间的物理距离被压缩,使天线之间产生较强的电磁耦合和干扰,进而造成整个阵列的有源驻波、效率、辐射方向图等重要性能的损失,最终导致系统性能,例如数据吞吐率的损失.文章介绍了多天线系统中的电磁干扰特性以及目前一系列的解决方案,并展望了未来多天线系统的发展方向及其对电磁干扰特性、电磁耦合特性调控技术的影响.     

5G天线对典型强电磁脉冲响应的对比分析

针对强电磁脉冲环境对5G通信系统的威胁,以5G天线为例,研究了典型电磁脉冲经天线口面耦合进入天线端口的电磁脉冲能量大小。利用电磁仿真软件分析了微带天线单元在高空核爆电磁脉冲、高功率微波以及超宽带电磁脉冲环境下天线馈电端口处感应的瞬态电压的时域和频域特性。仿真结果表明:高功率微波和超宽带电磁脉冲在天线单元馈电端口的感应电压较大,极易干扰甚至毁伤5G通信系统的射频后端。     

双频宽带双极化定向电磁偶极子天线设计

设计了一款双频带宽带双极化定向电磁偶极子天线。首先,采用最基本的电磁偶极子天线模型,通过对偶极子天线的形状进行调整以及增加Г形寄生枝节实现了双频段单极化定向电磁偶极子天线。其次,将两个单极化电磁偶极子天线十字交叉放置。最后,通过两个高度不同的Г形探针分别对两个天线进行耦合馈电,实现双频宽带双极化定向辐射特性。根据仿真结果,对天线模型进行了加工和测试。仿真和实测结果表明：天线在低频段0.8~0.96 GHz和高频段1.7~2.7 GHz内反射系数的模值均小于-10 dB,所对应端口隔离度分别大于20 dB和25 dB,天线的测试峰值增益在低频和高频段分别为5.5 dBi和8.2 dBi。该天线可应用在无线通讯系统中。     

车载天线射频系统的电磁兼容性研究北大核心CSCD

随着移动通讯频段的增加以及复杂电磁环境的影响，由于车载环境空间的局限性，必然导致车载天线增多、分布更加密集，从而使天线射频系统间发生相互干扰的可能性大大提高。针对车载天线射频系统存在的干扰问题，本文对FM单极子天线、VHF-UHF套筒单极子天线、GPS微带天线以及WIFI相控阵天线进行建模仿真计算。将所设计的天线与车辆模型结合，分析了几种天线在车载平台中的耦合问题，利用天线间耦合度优化车载天线布局。然后借助EMIT软件，建立车载天线的射频系统。利用干扰矩阵，系统间的频谱关系，研究天线射频系统的干扰问题，并利用滤波的方法极大程度的减小了天线射频系统间的干扰，对车载天线射频系统进行了优化。     

舰载多天线系统的耦合特性分析及防护

为解决舰载多天线系统间的电磁干扰问题,应用FEKO仿真软件进行了舰船与天线的全尺寸仿真模型;基于S参数原理与微波网络理论,给出了多天线系统的耦合度表达式;并分别计算了自由空间与舰船载体2种情况下,多天线耦合度的变化规律。结果表明,谐波、天线间距、天线频率及天线周围散射体是影响舰载多天线耦合特性的因素。并基于上述研究,给出了相应的电磁防护建议。本文研究成果可为后续共享铁塔电磁兼容性分析及多天线布局优化提供参考。     

一种低剖面贴片天线在相控阵系统中的应用

设计了一种低剖面口径耦合馈电形式的贴片天线,对该天线在相控阵系统中的应用进行了研究.该天线单元采用带状线馈电,抑制了馈电网络电磁泄漏,同时提高了天馈线的集成度;采取空气介质,改善了天线的表面波特性,简化天线结构.文中依次给出了该贴片单元的仿真设计、阵列样机的性能试验、辐射效率评估及应用举例,从仿真和试验结果中可以看出,该天线形式具有良好二维扫描驻波特性,带内辐射效率可达到90％,同时具有低剖面、结构简单等特点,适于用作高机动、轻量化相控阵雷达系统的辐射单元.     

可用于WLAN的双频MIMO天线设计

设计了一款可用于WLAN的双频MIMO天线。天线的正面为L型单极子,背面为金属接地板。通过在接地板上加载耦合枝节使天线具有双频特性。同时,为了天线的小型化,对耦合枝节进行了弯折处理,减小天线尺寸。在两个天线单元之间加载T型寄生枝节和刻蚀矩形缝隙来提高天线的隔离度。使用电磁仿真软件和矢量网络分析仪对天线进行仿真和实测,结果表明：天线的工作频段为2.4～2.55 GHz和5.1～6.3 GHz,覆盖了WLAN的频段,同时在低频段内隔离度高于19 dB,高频段内隔离度高于25 dB。此外,天线的包络相关系数小于0.01且具有全向辐射特性。天线整体性能较好,可以满足WLAN的需求。     

基于分形理论弯折线对称振子天线的研究

利用基于有限积分法的电磁仿真软件CST Microwave Studio对天线的谐振频率、谐振点输入阻抗、天线带宽、天线定向性等天线特性进行仿真研究,通过改变天线的几何形状找出它与天线特性参数之间的关系.结果表明,在不改变天线外部长度的情况下,通过改变天线的弯折次数、弯折角度、弯折高度、弯折置向等方法,可有效地降低天线的谐振频率,控制天线的输入参数,从而实现天线的电小化设计.这为分形天线的几何参数与电参数之间关系的研究提供理论依据与数据支持.     

一种改进的双频平面倒F天线

为了展宽PIFA天线的阻抗带宽,采用改变天线馈电结构的方法,应用电磁仿真软件进行仿真模拟,提出一种改进的、双频段、小型平面倒F天线(PIFA).讨论了馈电结构与天线结构参数对天线阻抗特性的影响,获得天线回波损耗小于-10 dB的相对带宽为10.54%(908~1009 MHz)及26.38%(2042~2662.5 MHz).天线在两个频段具有良好的辐射特性及增益特性,且该天线尺寸小、重量轻,适用于移动通信终端.     

具有辐射零点的高性能WiMAX频段微带滤波天线设计

本文基于滤波器综合方法,设计了一款工作在WiMAX频段的的高性能微带滤波天线。通过在谐振器之间引入电磁混合耦合,使得滤波天线的增益曲线在高频带出现了辐射零点,从而使得滤波天线具有良好的带外抑制特性。     

Design of compact fractal patch antenna for X/Ku/K-band applications

This paper presents a fractal-based compact new monopole antenna for wideband applications. The miniaturization has been achieved by incorporating Minkowski and Koch-snowflake fractals. The proposed antenna design is etched on top of Rogers RT/5880 dielectric material with a dimension of $8.10\times 8.10$ mm². The antenna is designed, analyzed, fabricated, and tested in the laboratory. The proposed geometry operates over a 8.62–22.40 GHz with fractional bandwidth (FBW) of 88.84% and VSWR is less than 2. The proposed monopole antenna exhibits nearly omnidirectional radiation patterns over the entire resonating band with a gain of 1–2.91 dBi and a radiation efficiency of more than 60.5%. Also, the measured results of the prototype make an excellent agreement with the simulated counterpart. Further, the antenna gives good time-domain characteristics. Therefore, the proposed miniaturized antenna can be used in X/Ku/K-band applications.     

一种小型宽带双极化5G基站天线

设计了一种适用于2G/3G/4G/5G移动通信的小型宽带±45°双极化基站天线。该天线由2对偶极子辐射片、2条微带馈线和1块反射板组成,辐射臂和微带馈线采用双面印刷工艺印刷在0.8 mm厚的FR4板,并固定放置于开有圆形槽的反射板上。对天线实物进行加工测试,测试结果表明,端口1工作频段为1.82～3.60 GHz,端口2工作频段为1.64～3.41 GHz;工作频段内,反射系数小于-10 dB,端口隔离度优于18 dB;交叉极化比在视轴方向大于17 dB,±60°方向大于15 dB;半功率波束65°左右,前后比优于18 dB,测试和仿真结果较吻合。所设计天线带宽宽,尺寸小,且制作工艺简单,成本低廉,适合批量生产,应用于5G移动通信基站中。     

SRR and S-shape slot loaded triple band notched UWB antenna

This paper demonstrates the design of a triple band notched ultrawideband circular microstrip patch antenna loaded with Complementary Split RingResonator (CSRR) and S-shaped slot in microstrip feed line. Complementary Split Ring Resonator slot and S-shaped slot are used to produce band notched characteristics for WiMAX band (3.30–3.60 GHz) and WLAN band (5.10–5.80 GHz) respectively. The downlink frequency band (7.25–7.75 GHz) of X-band for satellite communication is notched using Symmetrical Split Ring Resonator Pair (SSRRP) as electromagnetic coupling element near microstrip feed line which produces band stop characteristics. Measured results of fabricated antenna prototype are compared with simulated results and found in correspondence. The VSWR and vector current plots show evidence of the significant suppression in the desired frequency bands.     

Frequency-tunable open-ring microstrip antenna with optimally-positioned varactors for radiated-power in situ measurements

This paper presents a novel frequency-tunable open-ring microstrip antenna for radiated-power measurements in a real environment. In order to elevate the probing up to a few tens of meters, the antenna must have light-weight, narrow-bandwidth, and broad side-beam characteristics. An open-ring microstrip antenna is a good candidate for satisfying these requirements. Varactors are attached to tune the operation frequency, but the conventional position, which is in the vicinity of the ring-opening, shows a much lower gain and poor cross-polarization level. This paper proposes a superior position for the varactors, which is the upper-edge of the left and right sides of the ring. The reflection coefficient (S₁₁) in the simulation and experiment demonstrated that the resonant frequency can be increased by increasing the supply voltage. The proposed tunable antenna can be utilized in the probing apparatus to measure the radiated power.     

天线电磁兼容技术探讨

天线电磁兼容(EMC)问题,需要采用电磁场数值计算方法确定天线间的耦合度,据此来优化平台天线布局。文章从天线间距、方向图分布、极化、吸波材料运用、爬行波消除等方面,系统地总结了低副瓣天线、天线小型化、宽带天线、电磁带隙结构(EBG)等增强天线电磁兼容性的技术措施及适用范围。大型、复杂平台上的多天线电磁兼容问题,可结合实际情况选择一种或多种技术手段,实现天线间的电磁兼容。     

A printed dual-wideband magneto-electric dipole antenna for WWAN/LTE applications

A planar-printed dual-wideband U-shaped magneto-electric dipole omnidirectional antenna with a composite feeding structure for WWAN/LTE applications is proposed. Firstly, a U-shaped electric dipole structure is presented to provide a dual-wideband by changing the surface-current distributions. In addition, in order to reduce antenna size and improve impedance matching, a new feeding structure designed with inverted U-shaped tapered line and meandering T-shaped line is introduced. Finally, instead of a conventional vertical ground plane, a small-size one is printed on the reverse side of the substrate to achieve stable gains and omnidirectional radiation patterns. The antenna prototype can attain a bandwidth of 35.8% (0.78–1.12 GHz) with a stable gain of 3 ± 0.5 dBi for the lower band, and a bandwidth of 50.5% (1.66–2.78 GHz) with a gain of 3.8 ± 0.6 dBi for the upper band, covering the frequency bands granted for WWAN/LTE systems. To the best of our knowledge, it is the first real-sense planar magneto-electric dipole antenna proposed. In comparison with the existing ME dipole antennas, the proposed antenna, which is planar-printed on a small-size FR4 substrate with a simple structure, can be easily fabricated at low cost and thus is promising for WWAN/LTE communication.     

一种共面波导馈电的缝隙型超宽带天线

针对超宽带通信系统,提出一种小型超宽带天线,可以应用于终端设备。天线类型为共面波导馈电的缝隙型,缝隙结构为一矩形与一圆形组合而成,馈电结构与缝隙结构相似。天线的面积为22 mm×27 mm,印刷在厚度为0. 5 mm的FR4衬底上. 通过软件仿真分析了天线的工作原理以及尺寸对带宽的影响,仿真结果显示天线的带宽在不同的衬底厚度下均能覆盖UWB频段。天线的测试带宽为2.4 GHz~14.4 GHz,在超宽带的工作频段内测试效率超过76% ,测试增益大于2.1 dBi。     

双圆极化共形相控阵天线研究

设计了一种基于十字缝隙耦合双圆极化微带共形相控阵天线。首先设计了微带天线单元,分析了天线各结构参数对天线性能的影响。通过电桥向偏馈于十字缝隙上的馈线馈电,实现等幅、相差90°馈电,电桥的两个端口分别获得旋向相反的圆极化信号。然后对天线单元进行了测量,结果表明天线轴比小于3dB 的带宽为16%,驻波小于1.5 的带宽 为17%,波束宽度大于87°。最后对5×5 共形相控阵天线进行了仿真与测量,结果显示天线可以扫描60°,适合用作载体共形的卫星通信天线。     

A broadband helical saline water liquid antenna for wearable systems

A broadband helical liquid antenna made of saline water is proposed. A transparent hollow support is employed to fabricate the antenna. The rotation structure is fabricated with a thin flexible tube. The saline water with a concentration of 3.5% can be injected into or be extracted out from the tube to change the quantity of the solution. Thus, the tunability of the radiation pattern could be realised by applying the fluidity of the liquid. The radiation feature of the liquid antenna is compared with that of a metal one, and fairly good agreement has been achieved. Furthermore, three statements of the radiation performance corresponding to the ratio of the diameter to the wavelength of the helical saline water antenna have been proposed. It has been found that the resonance frequency increases when the length of the feeding probe or the radius of the vertical part of the liquid decreases. The fractional bandwidth can reach over 20% with a total height of 185 mm at 1.80 GHz. The measured results indicate reasonable approximation to the simulated. The characteristics of the liquid antenna make it a good candidate for various wireless applications, especially the wearable systems.     

一种新型小尺寸三陷波超宽带天线设计

文中提出了一种新型小尺寸具有三陷波特性的UWB天线。所设计的天线基本几何结构由50 Ω馈电线、圆形辐射贴片、缺陷地和一对开口谐振环组成,通过在天线的圆形辐射贴片上内嵌一对Y型贴片、地板上蚀刻出U型贴片和一对开口谐振环实现三陷波特性,天线的尺寸为30 mm×30 mm×16 mm。仿真和测试结果表明,该天线29~107 GHz的频段内回波损耗＜-10 dB,在37~42 GHz、515~5825 GHz和79~84 GHz3个频段内具有陷波特性,分别有效抑制了C频段的卫星系统、WLAN系统和X频段卫星系统对超宽带系统的干扰。在除3个阻带频段外的其余UWB工作频段范围内,有着良好的辐射方向特性和稳定的增益。仿真结果和实验结果表现出了良好的一致性。